Lighting device with plural fluorescent materials

ABSTRACT

Provided is a light-emitting device that has a high emission efficiency, excellent stability and temperature properties, and that generates light having a high color rendering property sufficient for practical use. This semiconductor light-emitting device comprises a semiconductor light-emitting element that emits blue light, a green phosphor that absorbs the blue light and emits green light, and an orange phosphor that absorbs the blue light and emits orange light, and is characterized in that the orange phosphor is an Eu-activated α-SiAlON phosphor having an emission spectrum peak wavelength within a range of 595 to 620 nm.

This application is a continuation of U.S. patent application Ser. No.13/979,554 filed Jul. 12, 2013, which is a U.S. national phase ofInternational Application No. PCT/JP2012/050065 filed Jan. 5, 2012,which claims priority to Japanese Patent Application No. 2011-008069filed Jan. 18, 2011 and Japanese Patent Application No. 2011-119337filed May 27, 2011, the entire contents of each of which are herebyincorporated by reference.

TECHNICAL FIELD

The present invention relates to a semiconductor light-emitting devicethat includes a fluorescent material and a semiconductor light-emittingelement.

BACKGROUND ART

Semiconductor light-emitting elements such as a light-emitting diode(LED) and the like have advantages that they are small, have a littlepower consumption, and are able to stably perform high brightness lightemission, and in recent years, a movement is ongoing to replaceillumination devices such as an incandescent light and the like withillumination devices using a light-emitting device that emits whitelight and includes an LED. As the LED that emits the white light, forexample, there is a combination of a blue LED and a Ce-activated YAGfluorescent material that is indicated by a composition formula of (Y,Gd)₃(Al, Ga)₅O₁₂:Ce.

In the light-emitting device having the above structure, the white lightis achieved by mixing of blue light from the LED and yellow light fromthe Ce-activated YAG fluorescent material as the fluorescent material.In this structure, a red color component is deficient because of a lightemission property of the Ce-activated YAG fluorescent material, and in acase of being used in a home illumination device and the like, forexample, a disadvantage that human skin colors look unnaturally and thelike occur.

Specifically, in the above light-emitting device, in a color temperatureregion defined by a neutral white color and a warm white color that areused in the illumination device, an average color rendering evaluationnumber (hereinafter, called Ra) is about 70 to about 75, and a specialcolor rendering evaluation number (hereinafter, called R9) indicatinghow the red color looks is about −40 to about −5, accordingly, when usedas an illumination device, the red color looks extremely poorly.

Because of this, to improve the above color rendering property such asRa, R9 and the like, a structure and the like are proposed, in whichbesides the above blue LED, a yellow fluorescent material such as a YAGfluorescent material and the like, a green fluorescent material and ared fluorescent material of a nitride relative and the like arecombined. Under the circumstances, a patent document 1 discloses a whitelight-emitting device that uses a blue LED as an excitation light sourceand is obtained by combining an orange fluorescent material and a greenfluorescent material that have a light emission wavelength of 560 to 590nm as a combination that has both high color rendering property andstability. Although not as a specific example of the whitelight-emitting device obtained by combining fluorescent materials, thisdocument discloses an α SiAlON fluorescent material and a β SiAlONfluorescent material as examples of the orange fluorescent material andthe green fluorescent material, respectively.

A patent document 2 discloses and proposes a combination of anEu-activated α SiAlON fluorescent material as the yellow fluorescentmaterial, an Eu-activated β SiAlON fluorescent material as the greenfluorescent material, and an Eu-activated CaAlSiN3 fluorescent materialas the red fluorescent material.

Besides, a non-patent document 1 shows a relationship between: Ra of awhite LED obtained by combining a fluorescent material and a blue LED;and a theoretical limit of luminous efficacy that indicates atheoretical limit of luminous efficiency of a light-emitting device. Anon-patent document 2 discloses a method that is described in thenon-patent document 1 and used to measure internal quantum efficiency ofa fluorescent material, and a non-patent document 3 disclosesEu-activated SrAlSiN₃ as an example of another kind of fluorescentmaterial that has a composition different from the fluorescent materialdisclosed in the present application.

CITATION LIST Patent Literature

-   PLT1: JP-A-2007-227928 (the publication date: Sep. 6, 2007)-   PLT2: JP-A-2006-261512 (the publication date: Sep. 28, 2006)

Non-Patent Literature

-   Non-patent document 1: K. Sakuma, “Efficiency Investigations of Blue    Light Excitation Type for White LEDs,” Proceedings of The 13th    International Display Workshops (IDE '06), PH 2-3, pp. 1221-1224,    Otsu, Japan (2006).-   Non-patent document 2: Kazuaki Okubo and others, “Absolute    Fluorescent Quantum Efficiency of NBS Phosphors Standard Samples,”    Journal from The Illuminating Engineering Institute of Japan, the    83th volume, the 2nd issue, p. 87 (1999).-   Non-patent document 3: H. Watanabe “Crystal structure and    luminescence properties of SrxCal-xAlSiN3: Eu2+mixed nitride    phosphors” Journal of Alloys and Compounds 475 (2009) 434-439.

SUMMARY OF INVENTION Technical Problem

However, according to the structure described in the patent document 1,as shown in the non-patent document 1, in the structure where Ra is 80or more, the theoretical limit of luminous efficacy decreasesremarkably, and the luminous efficiency of the light-emitting device isnot sufficient in practically useful color rendering property. On theother hand, according to the structure described in the patent document2, the wavelength of a light emission spectrum of the red fluorescentmaterial is a long wavelength, accordingly, the matching between theluminous efficacy curve of human and the light emission spectrum ispoor, and the red light emitted from the red fluorescent material looksdark for human eyes. Besides, the red light emitted from the redfluorescent material has a large wavelength shift from the blue lightthat is the excitation light, accordingly, the Stokes' loss is large,besides, the red fluorescent material easily absorbs light from thefluorescent material emitting at a wavelength shorter than the redlight, and it decreases the luminous efficiency to use the redfluorescent material in a semiconductor light-emitting device.

In other words, according to the structures described in the abovepatent documents 1 and 2, a disadvantage occurs in a case of beingapplied to a semiconductor light-emitting device that aims to achieveboth high brightness and high color rendering property.

Because of this, the present invention has been made in light of theabove problems, and it is an object of the present invention to providea light-emitting device that has sufficiently high color renderingproperty in practical use without using a red fluorescent material andis high in luminous efficiency.

Solution to Problem

As described above, to provide a light-emitting device that achieves thesufficiently high color rendering property in practical use and high inluminous efficiency, the inventors repeatedly produced prototypes of afluorescent material and a light-emitting device that uses thefluorescent material and a semiconductor light-emitting element. As aresult of this, the inventors found out that it is possible to provide alight-emitting device that solves the above problems and completed thepresent invention by means of a combination shown hereinafter.Hereinafter, details of the present invention are described.

The semiconductor light-emitting device according to the presentinvention includes: a semiconductor light-emitting element that emitsblue light; a green fluorescent material that absorbs the blue light toemit green light; an orange fluorescent material that absorbs the bluelight to emit orange light, wherein the orange fluorescent material isan Eu-activated α SiAlON fluorescent material that has a peak wavelengthof a light emission spectrum in a range of 595 to 620 nm.

According to the above structure, it becomes possible to achieve thelight-emitting device that has the sufficiently high color renderingproperty in practical use and is high in luminous efficiency.

The semiconductor light-emitting device according to the presentinvention is characterized in that the above Eu-activated α SiAlON is anEu-activated α SiAlON that is indicated by a general formula(Ca_(x)Eu_(y)) (Si_(12−(m+n)) Al_(m+n)) (O_(n)N_(16−n)) and designedwith a composition that meets:1.1≦x<2.0  (1)0<y<0.4  (2)1.5<x+y<2.0  (3)3.0≦m<4.0  (4)0≦n<y  (5)According to the above structure, it becomes possible to achieve thelight-emitting device in which the internal quantum efficiency of theEu-activated α SiAlON becomes high and the luminous efficiency is high.

The semiconductor light-emitting device according to the presentinvention is characterized in that the above Eu-activated α SiAlONfluorescent material is an Eu-activated α SiAlON fluorescent materialthat is indicated by a general formula (Ca_(x)Eu_(y)) (Si_(12−(m+n))Al_(m+n)) (O_(n)N_(16−n)) and designed with a composition that meets:1.1≦x<1.85  (1′)0.15<y<0.4  (2′)1.5<x+y<2.0  (3′)3.0≦m<4.0  (4′)0≦n<y  (5′)According to the above structure, it becomes possible to achieve thelight-emitting device in which the internal quantum efficiency of theEu-activated α SiAlON, whose peak wavelength of the light emissionspectrum is from 605 to 620 nm, becomes high and the luminous efficiencyis high.

The semiconductor light-emitting device according to the presentinvention is characterized in that the peak wavelength of the lightemission spectrum of the Eu-activated α SiAlON is from 605 to 620 nm.According to the above structure, it becomes possible to achieve thelight-emitting device that has higher color rendering property.

The semiconductor light-emitting device according to the presentinvention is characterized in that an average particle diameter of theEu-activated α SiAlON fluorescent material is 15 μm or more. Accordingto the above structure, it becomes possible to achieve thelight-emitting device that has higher color rendering property.

The semiconductor light-emitting device according to the presentinvention is characterized in that a specific surface area of theEu-activated α SiAlON fluorescent material is 0.4 m²/g or smaller.According to the above structure, it becomes possible to achieve thelight-emitting device that has higher luminous efficiency and highercolor rendering property.

The semiconductor light-emitting device according to the presentinvention is characterized in that a peak wavelength of a light emissionspectrum of the green fluorescent material is in a range of 520 nm to550 nm. According to the above structure, when composing alight-emitting device for emitting white light by combining the orangefluorescent material and a semiconductor light-emitting element foremitting blue light, the light emission spectrum of the light-emittingdevice matches the luminous efficacy curve of human, accordingly, itbecomes possible to achieve the light-emitting device that has higherluminous efficiency.

The semiconductor light-emitting device according to the presentinvention is characterized in that a half width of the light emissionspectrum of the green fluorescent material is 55 nm or smaller.According to the above structure, cross absorption between the orangefluorescent material and the green fluorescent material is alleviated,accordingly, it becomes possible to achieve the light-emitting devicethat is higher in luminous efficiency and high in color renderingproperty.

The semiconductor light-emitting device according to the presentinvention is characterized in that an absorptivity of the greenfluorescent material is 10% or smaller at 600 nm. According to the abovestructure, unnecessary absorption of the orange light by the greenfluorescent material is reduced, and it becomes possible to achieve thelight-emitting device that is higher in luminous efficiency.

The semiconductor light-emitting device according to the presentinvention is characterized in that the green fluorescent material is anEu-activated β SiAlON fluorescent material. According to the abovestructure, the internal quantum efficiency of the green fluorescentmaterial is high, and the chemical and physical stability is excellent,accordingly, it becomes possible to achieve the light-emitting devicethat is higher in luminous efficiency, high in stability andreliability.

The semiconductor light-emitting device according to the presentinvention is characterized in that an oxygen concentration of theEu-activated β SiAlON fluorescent material is in a range of 0.1 to 0.6%by weight. According to the above structure, the light emission spectrumof the Eu-activated β SiAlON has a short wavelength, accordingly, itbecomes possible to achieve the light-emitting device that is higher incolor rendering property.

Advantageous Effects of Invention

The semiconductor light-emitting device according to the presentinvention is composed by using, as the orange fluorescent material, theEu-activated α SiAlON fluorescent material that has the peak wavelengthof the light emission spectrum in the range of 595 to 620 nm, as aresult of this, it becomes possible to achieve the semiconductorlight-emitting device that has sufficiently high color renderingproperty and high color rendering property in practical use.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a sectional view showing a schematic structure of asemiconductor light-emitting device according to the present embodiment.

FIG. 2A is a graph showing a light emission spectrum of a fluorescentmaterial obtained in a production example 1-1.

FIG. 2B is a graph showing an excitation spectrum of the fluorescentmaterial obtained in the production example 1-1.

FIG. 3A is a graph showing a light emission spectrum of a fluorescentmaterial obtained in a production example 1-2.

FIG. 3B is a graph showing an excitation spectrum of the fluorescentmaterial obtained in the production example 1-2.

FIG. 4 is a graph showing a light emission spectrum of a fluorescentmaterial obtained in a production example 2-1.

FIG. 5 is a graph showing a light emission spectrum of a fluorescentmaterial obtained in a production example 2-2.

FIG. 6 is a graph showing a light emission spectrum of a fluorescentmaterial obtained in a production example 2-3.

FIG. 7 is a graph showing a light emission spectrum of a fluorescentmaterial obtained in a production example 2-4.

FIG. 8A is a graph showing a light emission spectrum of a fluorescentmaterial obtained in a comparative production example 1.

FIG. 8B is a graph showing an excitation spectrum of the fluorescentmaterial obtained in the comparative production example 1.

FIG. 9 is a graph showing a light emission spectrum of a fluorescentmaterial obtained in a comparative production example 2.

FIG. 10 is a graph showing a light emission spectrum of a light-emittingdevice obtained in an example 1.

FIG. 11 is a graph showing a light emission spectrum of a light-emittingdevice obtained in an example 2.

FIG. 12 is a graph showing a light emission spectrum of a light-emittingdevice obtained in an example 3.

FIG. 13 is a graph showing a light emission spectrum of a light-emittingdevice obtained in an example 4.

FIG. 14 is a graph showing a light emission spectrum of a light-emittingdevice obtained in an example 5.

FIG. 15 is a graph showing a light emission spectrum of a light-emittingdevice obtained in an example 6.

FIG. 16 is a graph showing a light emission spectrum of a light-emittingdevice obtained in an example 7.

FIG. 17 is a graph showing a light emission spectrum of a light-emittingdevice obtained in an example 8.

FIG. 18 is a graph showing a light emission spectrum of a light-emittingdevice obtained in an example 9.

FIG. 19 is a graph showing a light emission spectrum of a light-emittingdevice obtained in an example 10.

FIG. 20 is a graph showing a light emission spectrum of a light-emittingdevice obtained in an example 11.

FIG. 21 is a graph showing a light emission spectrum of a light-emittingdevice obtained in an example 12.

FIG. 22 is a graph showing a light emission spectrum of a light-emittingdevice obtained in an example 13.

FIG. 23 is a graph showing a light emission spectrum of a light-emittingdevice obtained in an example 14.

FIG. 24 is a graph showing a light emission spectrum of a light-emittingdevice obtained in an example 15.

FIG. 25 is a graph showing a light emission spectrum of a light-emittingdevice obtained in a comparative example 1.

FIG. 26 is a graph showing a light emission spectrum of a light-emittingdevice obtained in a comparative example 2.

FIG. 27 is a graph showing a light emission spectrum of a light-emittingdevice obtained in a comparative example 3.

FIG. 28 is a graph showing a light emission spectrum of a light-emittingdevice obtained in a comparative example 4.

FIG. 29 is a graph showing a light emission spectrum of a light-emittingdevice obtained in a comparative example 5.

FIG. 30 is a graph showing a light emission spectrum of a light-emittingdevice obtained in a comparative example 6.

FIG. 31 is a graph showing a relationship between Ra and the theoreticallimit efficiency of the semiconductor light-emitting devices produced inthe examples 1 to 8 and produced in the comparative examples 1 to 3.

FIG. 32 is a graph showing a relationship between Ra and the theoreticallimit efficiency of the semiconductor light-emitting devices produced inthe examples 9 to 15 and produced in the comparative examples 4 to 6.

FIG. 33 is a graph showing a light emission spectrum of a light-emittingdevice obtained in a comparative example 7.

FIG. 34 is a graph showing a light emission spectrum of a light-emittingdevice obtained in a comparative example 8.

FIG. 35 is a graph showing a light emission spectrum of a light-emittingdevice obtained in a comparative example 9.

FIG. 36 is a graph showing a light emission spectrum of a light-emittingdevice obtained in a comparative example 10.

FIG. 37 is a graph showing a relationship between Ra and the lightemission peak wavelength of the orange fluorescent materials of thesemiconductor light-emitting devices produced in the examples 1 to 8 andproduced in the comparative examples 1, 7 to 9.

FIG. 38 is a graph showing a relationship between Ra and the theoreticallimit efficiency of the semiconductor light-emitting devices produced inthe examples 1 to 8 and produced in the comparative examples 1, 7 to 10.

DESCRIPTION OF EMBODIMENTS

An embodiment of the present invention is described as follows. In themeantime, in the present specification, the term “A to B” indicating arange means to be A or more to B or small. Besides, various propertiesdescribed in the present specification mean values measured by methodsexplained in examples described later unless otherwise specified.

FIG. 1 is a sectional view showing a schematic structure of asemiconductor light-emitting device according to the present embodiment.The semiconductor light-emitting device 1 according to the presentembodiment includes: a semiconductor light-emitting element 2 that emitsblue light; an orange fluorescent material 13 that absorbs the bluelight to emit orange light; and a green fluorescent material 14 thatabsorbs the blue light to emit green light. Here, in the presentspecification, the blue light means light that has a peak wavelength ofa light emission spectrum in a wavelength range of 420 to 480 nm; thegreen light means light that has a peak wavelength of a light emissionspectrum in a wavelength range of 500 to 550 nm; the orange light meanslight that has a peak wavelength of a light emission spectrum in awavelength range of 560 to 620 nm; and the red light means light thathas a peak wavelength of a light emission spectrum in a wavelength rangeof 630 to 680 nm. Besides, the green fluorescent material means asubstance that is excited by the above blue light to emit the abovegreen light; the orange fluorescent material means a substance that isexcited by the above blue light to emit the above orange light; and thered fluorescent material means a substance that is excited by the aboveblue light to emit the above red light.

And, the above orange fluorescent material 13 is an Eu-activated αSiAlON fluorescent material that has the peak wavelength of the lightemission spectrum of 595 nm or more. By selecting suitable blue lightemitted from the semiconductor light-emitting element 2 and suitablegreen light emitted from the green fluorescent material 14 by means ofthe Eu-activated α SiAlON fluorescent material, it becomes possible toachieve the light-emitting device in which Ra, R9 have preferable valuesin practical use; the theoretical limit of luminous efficacy isextremely higher than the conventional known ones; and which is usefulin practical use.

Accordingly, based on a design stance not to use the red fluorescentmaterial, the inventors adjusted the light emission spectrum of theEu-activated α SiAlON fluorescent material, that is, the above orangefluorescent material combined with the green fluorescent material andstudied to improve color rendering performance. As a result of this, itwas found out that by using the Eu-activated α SiAlON in which the lightemission spectrum has a wavelength longer than the structures describedin the non-patent document 1, the patent documents 1 and 2, it ispossible to achieve the light-emitting device that has sufficient colorrendering property in practical use without using the red fluorescentmaterial and a preferable range of the light emission peak wavelength ofthe Eu-activated α SiAlON fluorescent material is 595 nm or more.

Here, sufficient values of the above Ra, R9 in practical use areintended to replace indoor illumination devices such as a fluorescentlamp and the like with the semiconductor light-emitting device. Atpresent, in a three-wavelength fluorescent lamp that is the most commonas the indoor illumination fluorescent lamp, Ra=81 or around, R9=26 oraround, besides, the JIS Z9125:2007 recommends an illumination devicehaving Ra of 80 or more as an illumination device for use in a room forwork and a long stay.

Besides, the above theoretical limit efficiency is defined in thenon-patent document 1 and is a theoretical limit of the luminousefficiency (lumen per watt: 1 m/W) of a light-emitting device that iscalculated based on the light emission spectrum of the light-emittingdevice. When calculating the theoretical limit of luminous efficacy, itis assumed that conversion efficiency from power for the semiconductorlight-emitting element to the blue light is 100%; and the internalquantum efficiency (IQE) of the fluorescent material is also 100%, andonly the Stokes' shift loss due to the wavelength conversion by thefluorescent material is considered as a loss. In other words, it issayable that in the light-emitting device which is composed by thesemiconductor light-emitting element emitting excitation light and thefluorescent material excited by the excitation light to emit fluorescentlight, the efficacy is the efficiency calculated by considering thetheoretically unavoidable loss only caused by the wavelength conversionfrom the excitation light to the fluorescent light. In the meantime, theinternal quantum efficiency of the fluorescent material can be measuredby the method described in the non-patent document 2 (Kazuaki Okubo andothers, “Absolute Fluorescent Quantum Efficiency of NBS PhosphorsStandard Samples,” Journal from The Illuminating Engineering Instituteof Japan, the 83th volume, the 2nd issue, p. 87 (1999).

In FIG. 1, as to the semiconductor light-emitting device 1, thesemiconductor light-emitting element 2 is placed on a printed wiringboard 3 that is a base board, a mold resin 5 formed of alight-transmissive resin, in which the above orange fluorescent material13 and the above green fluorescent material 14 are dispersed, is filledinside a resin frame 4 placed on the same printed wiring board 3,whereby the semiconductor light-emitting element 2 is encapsulated.

The above semiconductor light-emitting element 2 has an InGaN layer 6 asan active layer, and has a p-side electrode 7 and an n-side electrode 8with the InGaN layer 6 interposed therebetween; the n-side electrode 8is electrically connected to an n electrode portion 9, which is disposedfrom an upper surface to a rear surface of the printed wiring board 3,via an adhesive 10 that has electrical conductivity. Besides, the p-sideelectrode 7 of the semiconductor light-emitting element 2 iselectrically connected to a p electrode portion 11, which is disposedseparately from the above n electrode portion 9 from the upper surfaceto the rear surface of the printed wiring board 3, via a metal wire 12.

In the meantime, the semiconductor light-emitting device 1 according tothe present embodiment is not limited to the structure shown in FIG. 1,and it is possible to employ a structure of a conventionally knowngeneral semiconductor light-emitting device.

(I) Semiconductor Light-Emitting Element

In the present embodiment, the above semiconductor light-emittingelement 2 is a light-emitting diode (LED), however, is not limited tothe light-emitting diode (LED), and as the semiconductor light-emittingelement 2, it is possible to use conventionally known elements that emitblue light such as a semiconductor laser, an inorganic EL(electroluminescence) element and the like. In the meantime, as the LED,it is possible to use, for example, commercial products from Cree, Inc.and the like.

The light emission peak wavelength of the above semiconductorlight-emitting element 2 is not limited especially, however, ispreferable to be in a range of 440 nm to 470 nm from the viewpoint ofraising the luminous efficiency of the semiconductor light-emittingelement, and is more preferable to be in a range of 450 nm to 465 nmfrom the viewpoint of further raising the Ra, R9 values.

(II) Orange Fluorescent Material

The above orange fluorescent material 13 is an Eu-activated α SiAlONfluorescent material whose peak wavelength of the light emissionspectrum is in a range of 595 nm to 620 nm. If the light emission peakwavelength exceeds 620 nm, the internal quantum efficiency andtemperature property of the Eu-activated α SiAlON fluorescent materialtend to deteriorate, accordingly, 620 nm is set.

By setting the above peak wavelength of the light emission spectrum intothe above wavelength range, it is possible to achieve the semiconductorlight-emitting device that has sufficiently high color renderingproperty in practical use and is excellent especially in luminousefficiency, stability and temperature property.

As the above Eu-activated α SiAlON fluorescent material, as shown inJP-A-2005-307012 for example, it is possible to preferably use afluorescent material that is designed to have a low oxygen concentrationby using a nitride material as a start material. This is because the αSiAlON designed to have the low oxygen concentration has a highsolubility limit for elements Ca, Eu and the like other than Si, Al, Oand N, and easily takes these elements into the crystal.

A composition formula of the above Eu-activated α SiAlON fluorescentmaterial is indicated by a general formula (Ca_(x)Eu_(y)) (Si_(12−(m+n))Al_(m+n)) (O_(n)N_(16−n)) and designed with a composition that meets:1.1≦x<2.0  (1)0<y<0.4  (2)1.5<x+y<2.0  (3)3.0≦m<4.0  (4)0≦n<y  (5)

It is possible to produce the Eu-activated α SiAlON having thecomposition of the above (1) to (5) by using, for example, as the startmaterials, Ca₃N₂ as a Ca source, using AlN as an Al source, using Si₃N₄as an Si source, and using both Eu₂O₃ and EuN as an Eu source. The abovecomposition indicated by the above (1) to (5) is characterized by 0≦n<yand 1.5<x+y<2.0. Being 0≦n<y means that the oxygen concentration isdesigned to be lower than the Eu concentration. Being 1.5<x+y<2.0 meansthat the Ca concentration and the Eu concentration are designed to benear an upper limit concentration at which the α SiAlON single phase isobtained.

Besides, in the present invention, from the viewpoint of further raisingRa, R9, it is possible to use more preferably the Eu-activated α SiAlONfluorescent material having the peak wavelength of the light emissionspectrum of 605 nm to 620 nm, and the composition formula of thisEu-activated α SiAlON fluorescent material is indicated by a generalformula (Ca_(x)Eu_(y)) (Si_(12−(m+n)) Al_(m+n)) (O_(n)N_(16−n)) anddesigned with a composition that meets:1.1≦x<1.85  (1′)0.15<y<0.4  (2′)1.5<x+y<2.0  (3′)3.0≦m<4.0  (4′)0≦n<y  (5′)

It is possible to produce the Eu-activated α SiAlON having thecomposition of the above (1′) to (5′) by using, for example, as thestart materials, Ca₃N₂ as the Ca source, using AlN as the Al source,using Si₃N₄ as the Si source, and using both Eu₂O₃ and EuN as the Eusource. Besides, the above composition of the (1′) to (5′) ischaracterized in that the y value is large compared with the (1) to (5).The large y value means that the Eu concentration is designed high, andin the composition of (1′) to (5′), by designing the Eu concentrationhigh compared with the (1) to (5), the peak wavelength of the luminousefficiency of 605 nm to 620 nm is achieved.

Besides, in the production process of the above Eu-activated α SiAlONfluorescent material, as disclosed in JP-A-2009-96882 for example, it ispossible to preferably use a seed particle addition process to add an αSiAlON powder as a seed particle. This is because the α SiAlONfluorescent material designed to have the low oxygen concentration has alow oxygen concentration during a calcination time, accordingly, it ishard for a particle growth through a liquid phase to occur. Besides,also a rinse process by means of an acid treatment as shown inJP-A-2005-255855 can be preferably applied to the production process ofthe above Eu-activated α SiAlON.

It is preferable that the particle diameter of the above orangefluorescent material 14 is 1 μm to 50 μm, and is more preferable to be 5μm to 20 μm. Besides, it is preferable that the particle shape is asingle particle rather than an aggregate, specifically, it is preferablethat the specific surface area measured by an air permeability method is1 m²/g or smaller, more preferably 0.4 m²/g or smaller. For theseparticle diameter adjustment and particle shape adjustment, it ispossible to suitably use technologies such as mechanical smashing, grainboundary phase removing by the acid treatment, annealing and the like.Here, the air permeability method refers to a method generally called aLEA-NURSE method, and it is possible to obtain the specific surface areaby measuring a flow speed and pressure decline of air passing through asample filled layer.

In the meantime, as another nitride orange fluorescent material havingthe peak wavelength of the light emission spectrum of 620 nm or smaller,the non-patent document 3 discloses Eu-activated SrAlSiN₃ that is afluorescent material substance which has the peak wavelength of thelight emission spectrum of 610 nm, emits orange light with high internalquantum efficiency at blue excitation, and is chemically stable;however, compared with the Eu-activated α SiAlON fluorescent material,the Eu-activated SrAlSiN₃ has a high absorptivity in the green lightwavelength range and absorbs the green light emitted from the greenfluorescent material, accordingly, it is more preferable to use theEu-activated α SiAlON fluorescent material as the orange fluorescentmaterial.

(IV) Green Fluorescent Material

As the green fluorescent material 14, from the viewpoint of raising theluminous efficiency of the semiconductor light-emitting device, it ispossible to use a fluorescent material whose peak wavelength is in arange of 520 nm to 550 nm. If the peak wavelength of the light emissionspectrum of the green fluorescent material 14 is in the above range,when the light-emitting device 1 emitting the white light is composed bycombining the above orange fluorescent material 13 and the semiconductorlight-emitting element 2 emitting the blue light with each other, it ispossible to obtain a light emission spectrum that matches the luminousefficacy curve of human. Because of this, it becomes possible to achievethe light-emitting device that is high in luminous efficiency.

Besides, it is preferable that the above green fluorescent material 14has a half width of the light emission spectrum of 70 nm or smaller, andmore preferably has a half width in a range of 55 nm or smaller.Besides, a lower limit of the half width of the light emission spectrumof the above green fluorescent material 14 is not especially limited,however, preferably 15 nm or more.

When the half width of the light emission spectrum of the greenfluorescent material 14 is in the above range, the overlapping betweenthe absorption spectrum of the above orange fluorescent material 13 andthe light emission spectrum of the green fluorescent material 14 becomessufficiently small, accordingly, the green light absorption by theorange fluorescent material 13 is alleviated and it is possible toachieve the light-emitting device that is higher in luminous efficiency.

The above green fluorescent material 14 is not especially limited,however, for example, an Eu-activated oxynitride fluorescent material ispreferably used because of high stability and excellent temperatureproperty.

Further, because of being excellent in luminous efficiency among theEu-activated oxynitride fluorescent materials, an Eu-activated BSONfluorescent material shown in JP-A-2008-138156 and an Eu-activated βSiAlON fluorescent material shown in JP-A-2005-255895 are preferablyused.

Among the examples described as the above green fluorescent material 14,the Eu-activated β SiAlON fluorescent material is excellent in stabilityand temperature property, besides, has an especially narrow half widthof the light emission spectrum, and shows an excellent light emissionproperty.

It is preferable that a composition of the above Eu-activated BSONfluorescent material is Ba_(r)′ Eu_(x)′ O_(v)′ N_(w)′ (where 0≦y′≦3,1.6≦y′+x′≦3, 5≦u′≦7, 9<v′<15, 0<w′≦4) and a more preferable range of theabove y′, x′, u′, v′, and w′ is 1.5≦y′≦3, 2≦y′+x′≦3, 5.5≦u′≦7, 10<v′<13,and 1.5<w′≦4.

Besides, it is preferable that a composition of the above Eu-activated βSiAlON fluorescent material is Si_(6−z′) Al_(z′) O_(z′) N_(8−z′) (where0<z′<4.2), and a more preferable range of z′ is 0<z′<0.5.

Besides, the above Eu-activated β SiAlON has preferably an oxygenconcentration range of 0.1 to 0.6% by weight, and has more preferably anAl concentration of 0.13 to 0.8% by weight. When the Eu-activated βSiAlON fluorescent material is in these ranges, the half width of thelight emission spectrum tends to become narrow.

In the meantime, as to the Eu-activated β SiAlON fluorescent materialdisclosed in the international publication no. WO2008/062781, theflorescer's damaged phase is removed after calcination bypost-treatments such as the acid treatment and the like, accordingly,unnecessary absorption is slight and the light emission efficiency ishigh. Further, the Eu-activated β SiAlON fluorescent material disclosedin JP-A-2008-303331 has an oxygen concentration of 0.1 to 0.6% byweight, the half width of the light emission spectrum becomes narrow,which is preferable.

As the above green fluorescent material 14, more specifically, it ispossible to preferably use a fluorescent material which has a lightabsorptivity of 10% or smaller at 600 nm that is in a wavelength regionhaving no contribution to the light emission of the β SiAlON fluorescentmaterial and is near the peak wavelength of the above orange fluorescentmaterial.

It is preferable that the particle diameter of the above greenfluorescent material 14 is 1 μm to 50 μm, and is more preferable to be 5μm to 20 μm. Besides, it is preferable that the particle shape is asingle particle rather than an aggregate, specifically, it is preferablethat the specific surface area is 1 m²/g or smaller, more preferably 0.4m²/g or smaller. For these particle diameter adjustment and particleshape adjustment, it is possible to suitably use the technologies suchas mechanical smashing, grain boundary phase removing by the acidtreatment, annealing and the like.

Besides, in the case where the green fluorescent material 14 used in thepresent embodiment is the Eu-activated oxynitride fluorescent material,both the green fluorescent material 14 and the orange fluorescentmaterial 13 are oxynitrides, accordingly, the temperature dependencies,specific gravities, particle diameters and the like of the two kinds offluorescent materials have values approximate to each other. Because ofthis, when the above semiconductor light-emitting element is formed, itbecomes possible to perform the production with a good yield. Inaddition, the oxynitride fluorescent material has strong covalentbonding of the host crystal, accordingly, especially has slighttemperature dependency, and is durable to a chemical and physicaldamage, therefore, serves as a light-emitting element that is notinfluenced by a surrounding environment and has high stability andreliability.

Besides, as other green fluorescent materials, it is possible to useconventionally known fluorescent materials such as: a Ce-activatedaluminate garnet fluorescent material expressed by (Re_(1−x)Gd_(x)) 3(Al_(1−y)Ga_(y))₅O₁₂:Ce (Re=Y, Lu, Tb, 0≦x≦1, 0≦y≦1); a Ce-activatedsilicate garnet fluorescent material expressed by (Ca, Mg)₃Sc₂Si₃O₁₂:Ce;an Eu-activated alkaline earth silicon oxynitride fluorescent materialexpressed by MSi₂O₂N₂: Eu (M=Ba, Ca, Sr, Mg); an Eu-activated alkalineearth silicate fluorescent material expressed by M₂SiO₄: Eu (M=Ba, Ca,Sr, Mg) and the like.

(V) Mold Resin

In the above semiconductor light-emitting device 1, the mold resin 5used to encapsulate the semiconductor light-emitting element 2 isobtained by dispersing the above orange fluorescent material 13 and theabove green fluorescent material 14 into, for example, alight-transmissive resin such as a silicone resin, an epoxy resin andthe like. The dispersion method is not especially limited, and it ispossible to employ a conventionally known method.

A mixing ratio of the orange fluorescent material 13 and the greenfluorescent material 14 dispersed is not especially limited, and issuitably decidable such that a spectrum indicating a desired white pointis obtained.

For example, it is possible to set a mass ratio of thelight-transmissive resin to the orange fluorescent material 13 and greenfluorescent material 14 (the mass of the light-transmissive resin/(theorange fluorescent material 13+the green fluorescent material 14)) intoa range of 1 to 15. Further, it is possible to set a mas ratio of thegreen fluorescent material 14 to the orange fluorescent material 13 (themass ratio of (the green fluorescent material 14/the orange fluorescentmaterial 13)) into a range of 0.5 to 4.

(VI) Others

In the semiconductor light-emitting device according to the presentembodiment, as to the printed wiring board 3, the adhesive 10, the metalwire 12 and the like other than the semiconductor light-emitting element2, the orange fluorescent material 13, the green fluorescent material 14and the mold resin 5, it is possible to use the same structure asconventional technologies (e.g., JP-A-2003-321675, JP-A-2006-8721 andthe like) and it is possible to perform the production in the same wayas the conventional technologies.

EXAMPLES

Hereinafter, the present invention is described in more detail withreference to examples and comparative examples, however, the presentinvention is not limited to these examples.

[1] Fluorescent Material Production

Hereinafter, production methods and properties of respective fluorescentmaterials used in the examples and comparative examples are described.Besides, a table 1 shows a list of chemical formulae, fluorescentmaterial properties, applications of the examples·comparative examplesof the respective fluorescent materials (production examples 1-1 to 1-3,2-1 to 2-4, comparative production examples 1, 2).

TABLE 1 LIGHT EMISSION PEAK HALF WAVELENGTH (WIDTH) FLUORESCENT MATERIALCHEMICAL FORMULA (nm) (nm) PRODUCTION ORANGE Eu-ACTIVATED α(Ca_(1.8)Eu_(0.075))(Si_(8.2)Al_(3.8))(O_(0.05)N_(15.95)) 597 93 EXAMPLE1-1 COLOR SiAlON PRODUCTION ORANGE Eu-ACTIVATED α(Ca_(1.7)Eu_(0.2))(Si_(8.2)Al_(3.8))N₁₆ 610 92 EXAMPLE 1-2 COLOR SiAlONPRODUCTION ORANGE Eu-ACTIVATED α (Ca_(1.7)Eu_(0.2))(Si_(8.2)Al_(3.8))N₁₆610 92 EXAMPLE 1-3 COLOR SiAlON PRODUCTION GREEN Eu-ACTIVATED βSi_(5.77)Al_(0.23)O_(0.23)N_(7.77)Eu_(0.013) 540 53 EXAMPLE 2-1 COLORSiAlON PRODUCTION GREEN Eu-ACTIVATED βSi_(5.94)Al_(0.06)O_(0.06)N_(7.94)Eu_(0.014) 528 51 EXAMPLE 2-2 COLORSiAlON PRODUCTION GREEN Eu-ACTIVATED BSONBa_(2.07)Eu_(0.13)Si₇O_(10.2)N₄ 528 69 EXAMPLE 2-3 COLOR PRODUCTIONGREEN Ce-ACTIVATED Lu_(2.7)Ce_(0.3)Al₅O₁₂ 540 110 EXAMPLE 2-4 COLORLu₃Al₅O₁₂ ((Lu_(3−x)Ce_(x))Al₅O₁₂) COMPARATIVE ORANGE Eu-ACTIVATED(Ca_(0.75)Eu_(0.08))(Si_(9.38)Al_(2.62))(O_(0.95)N_(15.05)) 585 94PRODUCTION COLOR α SiAlON EXAMPLE 1 COMPARATIVE RED Eu-ACTIVATEDCa_(0.992)Eu_(0.008)SiAlN₃ 649 90 PRODUCTION COLOR CaAlSiN₃ EXAMPLE 2LIGHT INTERNAL ABSORPTIVITY QUANTUM CHROMA- @600 nm EFFICIENCY TICITYCOMPARATIVE (%) (%) x y EXAMPLE EXAMPLE PRODUCTION — 71 0.559 0.438EXAMPLE — EXAMPLE 1-1 1, 3, 5, 7, 10, 12, 14 PRODUCTION — 70 0.587 0.411EXAMPLE 2, 4, 6, — EXAMPLE 1-2 8, 9, 11, 13, 15 PRODUCTION — 70 0.5870.411 EXAMPLE 16 — EXAMPLE 1-3 PRODUCTION 9.1 73 0.325 0.644 EXAMPLE 1,2, 9 COMPARATIVE EXAMPLE 2-1 EXAMPLE 1~6 PRODUCTION 12.5  69 0.289 0.674EXAMPLE 3, COMPARATIVE EXAMPLE 2-2 4, 10, 11 EXAMPLE 7 PRODUCTION 8.2 720.287 0.623 EXAMPLE 5, COMPARATIVE EXAMPLE 2-3 6, 12, 13 EXAMPLE 8PRODUCTION 9.3 73 0.420 0.554 EXAMPLE 7, COMPARATIVE EXAMPLE 2-4 8, 14,15 EXAMPLE 9 COMPARATIVE — 73 0.509 0.484 — COMPARATIVE PRODUCTIONEXAMPLE EXAMPLE 1 1, 2, 4, 5, 7, 8, 9 COMPARATIVE — 80 0.657 0.340 —COMPARATIVE PRODUCTION EXAMPLE EXAMPLE 2 2, 3, 5, 6

Production Example 1-1: Production 1 of Orange Fluorescent Material(Eu-Activated α SiAlON Fluorescent Material)

To obtain a fluorescent material in which x=1.8, y=0.075, m=3.75, n=0.05in the composition formula (Ca_(x)Eu_(y)) (Si_(12−(m+n)) Al_(m+n))(O_(n)N_(16−n)), weighing is performed to obtain, as raw materialpowders, 59.8 mass % of α type silicon nitride powder, 24.3 mass % ofaluminum nitride power, 13.9 mass % of calcium nitride powder, 0.9 mass% of europium oxide powder, and 1.1 mass % of europium nitride powder,and mixing is performed for 10 minutes or more by using a mortar andpestle formed of silicon nitride sintered body to obtain a powderaggregate. In the meantime, as the europium nitride, a synthetic, whichis obtained by nitriding metal europium in ammonia, is used.

The obtained powder aggregate is made to pass through a sieve having anaperture of 250 μm and filled into a crucible that has a size of 20 mmin diameter, 20 mm in height and is formed of boron nitride. In themeantime, all the respective processes of the weighing, mixing, andforming of the powder are performed in a glove compartment that is ableto hold a nitrogen atmosphere that contains water of 1 ppm or smallerand oxygen of 1 ppm or smaller.

Next, the crucible is set into a pressure electric furnace of graphiteresistance heating type; nitrogen having a purity of 99.999 volume % isintroduced to obtain a pressure of 1 MPa; the crucible is raised to1800° C. in 500° C. increments per hour, further kept at 1800° C. for 2hours, then, a heat treatment is performed. A product obtained by theheat treatment is smashed by means of an agate mortar, further, treatedat 60° C. in a 1:1 mixed acid of 50% of hydrofluoric acid and 96% ofconcentrated sulfuric acid, whereby a fluorescent material powder isobtained. Applying powder X ray diffraction measurement (XRD) to theobtained fluorescent material powder by using K α rays of Cu, it isfound out that the fluorescent material powder has an α SiAlON crystalstructure. Besides, as a result of casting light onto the fluorescentmaterial powder by means of a lamp that emits light having a wavelengthof 365 nm, it is confirmed that orange color light is emitted.

FIG. 2A is a graph showing a light emission spectrum of the obtainedfluorescent material powder; the vertical axis is the relative lightemission intensity (arbitrary unit), while the horizontal axis is thewavelength (nm). Besides, FIG. 2B is a graph showing an excitationspectrum of the obtained fluorescent material powder; the vertical axisis the relative light emission intensity (arbitrary unit), while thehorizontal axis is the wavelength (nm).

In the meantime, the excitation spectrum and light emission spectrum ofthe fluorescent material powder shown in FIG. 2A and FIG. 2B are resultsof measurement using the F-4500 (from Hitachi, Ltd.). The light emissionspectrum is measured by performing the excitation by means of light of450 nm, while the excitation spectrum is measured by scanning theintensity of the light emission peak. As to the chromaticity coordinatesof the light emission spectrum shown in FIG. 2A, (x, y)=(0.559, 0.438),the peak wavelength is 597 nm, and the half width is 93 nm.

Besides, the internal quantum efficiency of the fluorescent materialshown in the present production example 1-1, which is measured by ameasurement system obtained by combining the MCPD-7000 and anintegrating sphere with each other, is 71%.

Further, the specific surface area of the obtained fluorescent materialpowder, which is measured by the LEA-NURSE from TSUTSUI SCIENTIFICINSTRUMENTS, CO., LTD., is 0.36 m²/g, and the average particle diameter,which is measured by an SEM image observed by the VE- from KEYENCECORPORATION, is 16.2 μm.

Production Example 1-2: Production 2 of Orange Fluorescent Material(Eu-Activated α SiAlON Fluorescent Material)

To obtain a fluorescent material in which x=1.7, y=0.2, m=3.8, n=0 inthe composition formula (Ca_(x)Eu_(y)) (Si_(12−(m+n))Al_(m+n))(O_(n)N_(16−n)), weighing is performed to obtain, as raw materialpowders, 58.4 mass % of a type silicon nitride powder, 23.7 mass % ofaluminum nitride power, 12.8 mass % of calcium nitride powder, and 5.1mass % of europium nitride powder, and mixing is performed for 10minutes or more by using a mortar and pestle formed of silicon nitridesintered body to obtain a powder aggregate.

The obtained powder aggregate is made to pass through a sieve having anaperture of 250 μm and filled into a crucible that has a size of 20 mmin diameter, 20 mm in height and is formed of boron nitride. In themeantime, all the respective processes of the weighing, mixing, andforming of the powder are performed in a glove compartment that is ableto hold a nitrogen atmosphere that contains water of 1 ppm or smallerand oxygen of 1 ppm or smaller.

Next, the crucible is set into a pressure electric furnace of graphiteresistance heating type; nitrogen having a purity of 99.999 volume % isintroduced to obtain a pressure of 1 MPa; a heat treatment is performedsuch that the crucible is raised to 1800° C. in 500° C. increments perhour; further kept at 1800° C. for 2 hours. A product obtained by theheat treatment is smashed by means of an agate mortar, further, treatedat 60° C. in a 1:1 mixed acid of 50% of hydrofluoric acid and 96% ofconcentrated sulfuric acid, whereby a fluorescent material powder isobtained. Applying the powder X ray diffraction measurement (XRD) to theobtained fluorescent material powder by using K α rays of Cu, it isfound out that the fluorescent material powder has an α SiAlON crystalstructure. Besides, as a result of casting light onto the fluorescentmaterial powder by means of a lamp that emits light having a wavelengthof 365 nm, it is confirmed that orange color light is emitted.

FIG. 3A is a graph showing a light emission spectrum of the obtainedfluorescent material powder; the vertical axis is the relative lightemission intensity (arbitrary unit), while the horizontal axis is thewavelength (nm). Besides, FIG. 3B is a graph showing an excitationspectrum of the obtained fluorescent material powder; the vertical axisis the relative light emission intensity (arbitrary unit), while thehorizontal axis is the wavelength (nm).

In the meantime, the excitation spectrum and light emission spectrum ofthe fluorescent material powder shown in FIG. 3A and FIG. 3B are resultsof measurement using the F-4500 (from Hitachi, Ltd.). The light emissionspectrum is measured by performing the excitation by means of light of450 nm, while the excitation spectrum is measured by scanning theintensity of the light emission peak. As to the chromaticity coordinatesof the light emission spectrum shown in FIG. 3A, (x, y)=(0.587, 0.411),the peak wavelength is 610 nm, and the half width is 92 nm.

Besides, the internal quantum efficiency of the fluorescent materialshown in the present production example 1-2, which is measured by ameasurement system obtained by combining the MCPD-7000 and anintegrating sphere with each other, is 70%.

Further, the specific surface area of the obtained fluorescent materialpowder, which is measured by the LEA-NURSE from TSUTSUI SCIENTIFICINSTRUMENTS, CO., LTD., is 0.38 m²/g, and the average particle diameter,which is measured by an SEM image observed by the VE- from KEYENCECORPORATION, is 15.3 μm.

Production Example 1-3: Production 3 of Orange Fluorescent Material(Eu-Activated α SiAlON Fluorescent Material)

To obtain a fluorescent material in which x=1.7, y=0.2, m=3.8, n=0 inthe composition formula (Ca_(x)Eu_(y)) (Si_(12−(m+n)) Al_(m+n))(O_(n)N_(16−n)) that is the same design composition as the productionexample 1-2, a predetermined amount of raw material powder is weighed,and mixing is performed for 10 minutes or more by using a mortar andpestle formed of silicon nitride sintered body to obtain a powderaggregate.

The obtained powder aggregate is made to pass through a sieve having anaperture of 250 μm and filled into a crucible that has a size of 20 mmin diameter, 20 mm in height and is formed of boron nitride. In themeantime, all the respective processes of the weighing, mixing, andforming of the powder are performed in a glove compartment that is ableto hold a nitrogen atmosphere that contains water of 1 ppm or smallerand oxygen of 1 ppm or smaller.

Next, the crucible is set into a pressure electric furnace of graphiteresistance heating type; nitrogen having a purity of 99.999 volume % isintroduced to obtain a pressure of 1 MPa; the crucible is raised to1700° C. in 500° C. increments per hour, further kept at 1700° C. for 2hours, then, a heat treatment is performed. A product obtained by theheat treatment is smashed by means of an agate mortar, further, treatedat 60° C. in a 1:1 mixed acid of 50% of hydrofluoric acid and 96% ofconcentrated sulfuric acid, whereby a fluorescent material powder isobtained. Applying the powder X ray diffraction measurement (XRD) to theobtained fluorescent material powder by using K α rays of Cu, it isfound out that the fluorescent material powder has an α SiAlON crystalstructure. Besides, as a result of casting light onto the fluorescentmaterial powder by means of a lamp that emits light having a wavelengthof 365 nm, it is confirmed that orange color light is emitted. The lightemission properties of the obtained powder such as the light emissionspectrum, the excitation spectrum and the like are the same as theorange fluorescent material obtained in the production example 1-2.

Further, the specific surface area of the obtained fluorescent materialpowder, which is measured by the LEA-NURSE from TSUTSUI SCIENTIFICINSTRUMENTS, CO., LTD., is 0.78 m²/g, and the average particle diameter,which is measured by an SEM image observed by the VE- from KEYENCECORPORATION, is 11.2 μm.

Production Example 2-1: Production of Green Fluorescent Material(Eu-Activated β SiAlON Fluorescent Material)

To obtain an Eu-activated β SiAlON fluorescent material in which z′=0.23in a composition formula expressed by Si_(6−z′)Al_(z′)O_(z′)N_(8−z′) andEu is activated by 0.09 at. %, weighing is performed to obtain acomposition of 95.82 mass % of α type silicon nitride powder, 3.37 mass% of aluminum nitride power, and 0.81 mass % of europium oxide powder,and mixing is performed for 10 minutes or more by using a mortar andpestle formed of silicon nitride sintered body to obtain a powderaggregate. This powder aggregate is made to free-fall to be filled intoa crucible formed of boron nitride.

Next, the crucible is set into a pressure electric furnace of graphiteresistance heating type; the calcination atmosphere is vacuumed by adiffusion pump; the crucible is heated from a room temperature to 800°C. in 500° C. increments per hour; nitrogen having a purity of 99.999volume % is introduced at 800° C. to obtain a pressure of 1 MPa;thereafter, the crucible is raised to 1900° C. in 500° C. increments perhour, further kept at the temperature for 8 hours to obtain afluorescent material sample. The obtained fluorescent material sample issmashed by means of an agate mortar, further, treated at 60° C. in a 1:1mixed acid of 50% of hydrofluoric acid and 70% of nitric acid, whereby afluorescent material powder is obtained.

Applying the powder X ray diffraction measurement (XRD) to the obtainedfluorescent material powder by using K α rays of Cu, it is found outthat the fluorescent material powder has a β type SiAlON structure.Besides, as a result of casting light onto the fluorescent materialpowder by means of a lamp that emits light having a wavelength of 365nm, it is confirmed that green color light is emitted.

As a result of measuring a light emission spectrum by using the F-4500(from Hitachi, Ltd.) when exciting the powder of the obtainedEu-activated β SiAlON fluorescent material by means of light of 450 nm,the light emission spectrum shown in FIG. 4 is obtained. In FIG. 4, thevertical axis is the light emission intensity (arbitrary unit), whilethe horizontal axis is the wavelength (nm).

As to the chromaticity coordinates of the light emission spectrum shownin FIG. 4, (x, y)=(0.325, 0.644), the peak wavelength is 540 nm, and thehalf width is 53 nm. Besides, the light absorptivity at a wavelength of600 nm, which is measured by using the MCPD-7000 (from OtsukaElectronics Co., Ltd.), is 9.1%.

Besides, the internal quantum efficiency of the fluorescent materialshown in the present production example 2-1, which is measured by ameasurement system obtained by combining the MCPD-7000 and anintegrating sphere with each other, is 73%.

Further, the specific surface area of the obtained fluorescent materialpowder, which is measured by the LEA-NURSE from TSUTSUI SCIENTIFICINSTRUMENTS, CO., LTD., is 0.80 m²/g, and the average particle diameter,which is measured by an SEM image observed by the VE- from KEYENCECORPORATION, is 9.2 μm.

Production Example 2-2: Adjustment 2 of Eu-Activated β SiAlONFluorescent Material

To obtain an Eu-activated β SiAlON fluorescent material in which z′=0.06in the composition formula expressed by Si_(6−z′)Al_(z′)O_(z′)N_(8−z)′and Eu is activated by 0.10 at. %, a predetermined amount is weighed toobtain a composition of 93.59 weight % of metal Si powder, 5.02 weight %of aluminum nitride power, and 1.39 weight % of europium oxide powderthat have passed through a sieve of 45 μm, and mixing is performed for10 minutes or more by using a mortar and pestle formed of siliconnitride sintered body to obtain a powder aggregate. This powderaggregate is made to free-fall into a crucible formed of boron nitridethat has a size of 20 mm in diameter, 20 mm in height.

Next, the crucible is set into a pressure electric furnace of graphiteresistance heating type; the calcination atmosphere is vacuumed by adiffusion pump; the crucible is heated from a room temperature to 800°C. at a speed of 500° C. increments per hour; nitrogen having a purityof 99.999 volume % is introduced at 800° C. to obtain a pressure of 0.5MPa; the crucible is raised to 1300° C. in 500° C. increments per hour,thereafter, raised to 1600° C. in 1° C. increments per minute and keptat the temperature for 8 hours. The synthesized sample is smashed bymeans of an agate mortar into a powder to obtain a powder sample.

Next, the heat treatment is reapplied to the powder. The powder calcinedat 1600° C. is smashed by using a mortar and pestle formed of siliconnitride sintered body, thereafter, is made to free-fall into a cruciblethat is formed of boron nitride and has a size of 20 mm in diameter, 20mm in height.

The crucible is set into a pressure electric furnace of graphiteresistance heating type; the calcination atmosphere is vacuumed by adiffusion pump; the crucible is heated from a room temperature to 800°C. at a speed of 500° C. increments per hour; nitrogen having a purityof 99.999 volume % is introduced at 800° C. to obtain a pressure of 1MPa; thereafter, the crucible is raised to 1900° C. in 500° C.increments per hour, further kept at the temperature for 8 hours toobtain a fluorescent material sample. The obtained fluorescent materialsample is smashed by means of an agate mortar, further, treated at 60°C. in a 1:1 mixed acid of 50% of hydrofluoric acid and 70% of nitricacid, whereby a fluorescent material powder is obtained.

Applying the powder X ray diffraction measurement (XRD) to thefluorescent material powder, it is found out that the fluorescentmaterial powder has a β type SiAlON structure. Besides, as a result ofcasting light onto the fluorescent material powder by means of a lampthat emits light having a wavelength of 365 nm, it is confirmed thatgreen color light is emitted.

As a result of measuring a light emission spectrum of the powder of theobtained Eu-activated β SiAlON fluorescent material, the light emissionspectrum shown in FIG. 5 is obtained. In FIG. 5, the vertical axis isthe light emission intensity (arbitrary unit), while the horizontal axisis the wavelength (nm). As to the chromaticity coordinates of the lightemission spectrum shown in FIG. 5, (x, y)=(0.289, 0.674), the peakwavelength is 528 nm, and the half width is 51 nm. Besides, measuring anoxygen amount contained in the synthetic powder by using anoxygen/nitrogen analyzer (the TC436 type from LECO Corporation) with acombustion method, the oxygen content is 0.4 weight %. Besides, thelight absorptivity at a wavelength of 600 nm, which is measured by usingthe MCPD-7000 (from Otsuka Electronics Co., Ltd.), is 12.5%.

Besides, the internal quantum efficiency of the fluorescent materialshown in the present production example 2-2, which is measured by ameasurement system obtained by combining the MCPD-7000 and anintegrating sphere with each other, is 69%.

Further, the specific surface area of the obtained fluorescent materialpowder, which is measured by the LEA-NURSE from TSUTSUI SCIENTIFICINSTRUMENTS, CO., LTD., is 0.83 m²/g, and the average particle diameter,which is measured by an SEM image observed by the VE- from KEYENCECORPORATION, is 10.3 μm.

Production Example 2-3: Production of Green Fluorescent Material(Eu-Activated BSON Fluorescent Material)

To obtain an fluorescent material having a composition formula expressedby Ba_(2.07)Eu_(0.13)Si₇O_(10.2)N₄, mixing is performed, by using anagate mortar and a pestle, to obtain a composition of 17.12 mass % of βtype silicon nitride powder, 29.32 mass % of silicon oxide powder, 50.75mass % of barium carbonate powder, and 2.81 mass % of europium oxidepowder, whereby 50 g of powder mixture is obtained. The obtained powdermixture is mixed in ethanol by means of a rolling ball mill that uses anagate ball and a nylon pot to obtain a slurry.

The obtained slurry is dried at 100° C. by means of an oven; theobtained powder aggregate is smashed by means of a dry rolling ball millthat uses an agate ball and a nylon pot, whereby micro-particles havingabout 10 μm in diameter are obtained. The obtained micro-particles arefilled into an aluminum crucible; a slight load is exerted to performcompression molding, thereafter, is calcined under a condition of 1100°C. for 3 hours in the air; the obtained calcined body is smashed bymeans of an agate mortar to obtain a precursor sample.

Next, the crucible is set into a pressure electric furnace of graphiteresistance heating type; the calcination atmosphere is vacuumed by adiffusion pump; the crucible is heated from a room temperature to 800°C. at a speed of 500° C. increments per hour; nitrogen having a purityof 99.999 volume % is introduced at 800° C. to obtain a pressure of 1MPa; thereafter, the crucible is raised to 1300° C. in 500° C.increments per hour, further kept at the temperature for 2 hours toobtain a fluorescent material sample. The obtained calcined matter issmashed by means of an agate mortar, filled again into the aluminumcrucible; a slight load is exerted to perform the compression molding,thereafter, is calcined under a condition of 1300° C. for 48 hours inthe nitrogen atmosphere; the obtained calcined substance is smashed bymeans of an agate mortar to obtain a fluorescent material powder.

Applying the powder X ray diffraction measurement (XRD) to the obtainedfluorescent material powder by using K α rays of Cu, all the obtainedcharts show that the fluorescent material powder has a BSON structure.Besides, as a result of casting light onto the fluorescent materialpowder by means of a lamp that emits light having a wavelength of 365nm, it is confirmed that green color light is emitted.

As a result of measuring a light emission spectrum when exciting, bymeans of the light of 450 nm, the powder of the obtained Eu-activatedBSON fluorescent material by using the F-4500 (from Hitachi, Ltd.), thelight emission spectrum shown in FIG. 6 is obtained. In FIG. 6, thevertical axis is the light emission intensity (arbitrary unit), whilethe horizontal axis is the wavelength (nm). As to the chromaticitycoordinates of the light emission spectrum shown in FIG. 6, (x,y)=(0.287, 0.623), the peak wavelength is 528 nm, and the half width is69 nm. Besides, the light absorptivity at a wavelength of 600 nm, whichis measured by using the MCPD-7000 (from Otsuka Electronics Co., Ltd.),is 8.2%.

Besides, the internal quantum efficiency of the fluorescent materialshown in the present production example 1, which is measured by ameasurement system obtained by combining the MCPD-7000 and anintegrating sphere with each other, is 72%.

Production Example 2-4: Adjustment of Green Fluorescent Material(Ce-Activated Lu₃Al₅O₁₂((Lu_(3−x)Ce_(x))Al₅O₁₂))

To obtain an fluorescent material having a composition formula expressedby Lu_(2.7)Ce_(0.3)Al₅O₁₂, weighing is performed in the air to obtain apredetermined composition of 63.7 weight % of Lu₂O₃ powder, 6.1 weight %of CeO₂ powder, and 30.2 weight % of Al₂O₃ powder, further, as acalcination assistant, a predetermined amount of BaF₂ is added; mixingis performed by means of a rolling ball mill that uses an agate ball anda nylon pot to obtain a powder mixture. The obtained mixture is filledinto a quartz crucible, calcined under a condition of 1400° C. for 5hours in a reduction atmosphere of N₂ (95%)+H₂ (5%); the obtainedcalcined substance is smashed by means of an agate mortar to obtain afluorescent material powder.

As a result of casting light onto the obtained Ce-activated Lu₃Al₅O₁₂fluorescent material powder by means of a lamp that emits light having awavelength of 365 nm, it is confirmed that green color light is emitted.As a result of measuring a light emission spectrum of the powder, thelight emission spectrum shown in FIG. 7 is obtained.

In FIG. 7, the vertical axis is the light emission intensity (arbitraryunit), while the horizontal axis is the wavelength (nm). As to thechromaticity coordinates of the light emission spectrum shown in FIG. 7,(x, y)=(0.420, 0.554), the peak wavelength is 540 nm, and the half widthis 110 nm. Besides, the light absorptivity at a wavelength of 600 nm,which is measured by using the MCPD-7000 (from Otsuka Electronics Co.,Ltd.), is 9.3%.

Besides, the internal quantum efficiency of the fluorescent materialshown in the present production example 2-4, which is measured by ameasurement system obtained by combining the MCPD-7000 and anintegrating sphere with each other, is 73%.

Comparative Production Example 1: Production of Eu-Activated α SiAlONFluorescent Material

To obtain a fluorescent material in which x=0.75, y=0.08, m=1.67, n=0.95in the composition formula (Ca_(x)Eu_(y)) (Si_(12−(m+n))Al_(m+n))(O_(n)N_(16−n)), weighing is performed to obtain, as raw materialpowders, 69.0 mass % of a type silicon nitride powder, 16.9 mass % ofaluminum nitride power, 11.8 mass % of calcium carbonate powder, and 2.3mass % of europium oxide powder, and mixing is performed for 10 minutesor more by using a mortar and pestle formed of silicon nitride sinteredbody to obtain a powder aggregate.

The obtained powder aggregate is made to pass through a sieve having anaperture of 250 μm and filled into a crucible that has a size of 20 mmin diameter, 20 mm in height and is formed of boron nitride. In themeantime, all the respective processes of the weighing, mixing, andforming of the powder are performed in a glove compartment that is ableto hold a nitrogen atmosphere that contains water of 1 ppm or smallerand oxygen of 1 ppm or smaller.

Next, the crucible is set into a pressure electric furnace of graphiteresistance heating type; nitrogen having a purity of 99.999 volume % isintroduced to obtain a pressure of 1 MPa; a heat treatment is performedsuch that the crucible is raised to 1800° C. in 500° C. increments perhour; further kept at 1800° C. for 2 hours. A product obtained by theheat treatment is smashed by means of an agate mortar, further, treatedin a 1:1 mixed acid of 50% of hydrofluoric acid and 96% of concentratedsulfuric acid, whereby a fluorescent material powder is obtained.Applying the powder X ray diffraction measurement (XRD) to the obtainedfluorescent material powder by using K α rays of Cu, it is found outthat the fluorescent material powder has an α SiAlON crystal structure.Besides, as a result of casting light onto the fluorescent materialpowder by means of a lamp that emits light having a wavelength of 365nm, it is confirmed that orange color light is emitted.

FIG. 8A is a graph showing a light emission spectrum of the obtainedfluorescent material powder; the vertical axis is the relative lightemission intensity (arbitrary unit), while the horizontal axis is thewavelength (nm). Besides, FIG. 8B is a graph showing an excitationspectrum of the obtained fluorescent material powder; the vertical axisis the relative light emission intensity (arbitrary unit), while thehorizontal axis is the wavelength (nm).

In the meantime, the excitation spectrum and light emission spectrum ofthe fluorescent material powder shown in FIG. 8A and FIG. 8B are resultsof measurement using the F-4500 (from Hitachi, Ltd.). The light emissionspectrum is measured by performing the excitation by means of light of450 nm, while the excitation spectrum is measured by scanning theintensity of the light emission peak. As to the chromaticity coordinatesof the light emission spectrum shown in FIG. 8A, (x, y)=(0.509, 0.484),the peak wavelength is 585 nm, and the half width is 94 nm.

Besides, the internal quantum efficiency of the fluorescent materialshown in the present production example 1, which is measured by ameasurement system obtained by combining the MCPD-7000 and anintegrating sphere with each other, is 73%.

Comparative Production Example 2: Production of Eu-Activated CaAlSiN₃Fluorescent Material

To obtain a fluorescent material having a composition formula expressedby Ca_(0.992)Eu_(0.008)SiAlN₃, weighing is performed to obtain 29.7 mass% of aluminum nitride power, 33.9 mass % of α type silicon nitridepowder, 35.6 mass % of calcium nitride powder, and 0.8 mass % ofeuropium nitride powder, and mixing is performed for 10 minutes or moreby using a mortar and pestle formed of silicon nitride sintered body toobtain a powder aggregate. As the europium nitride, a synthetic, whichis synthesized by nitriding metal europium in ammonia, is used. Thispowder aggregate is made to free-fall into a crucible formed of boronnitride that has a size of 20 mm in diameter, 20 mm in height. In themeantime, all the respective processes of the weighing, mixing, andforming of the powder are performed in a glove compartment that is ableto hold a nitrogen atmosphere that contains water of 1 ppm or smallerand oxygen of 1 ppm or smaller.

Next, the crucible is set into a pressure electric furnace of graphiteresistance heating type; nitrogen having a purity of 99.999 volume % isintroduced to obtain a pressure of 1 MPa; the crucible is raised to1800° C. in 500° C. increments per hour, further kept at 1800° C. for 2hours to obtain a fluorescent material sample. The obtained fluorescentmaterial sample is smashed by means of an agate mortar to obtain afluorescent material powder. Applying the powder X ray diffractionmeasurement (XRD) to the obtained fluorescent material powder by using Kα rays of Cu, it is found out that the fluorescent material powder has aCaAlSiN₃ crystal structure. Besides, as a result of casting light ontothe fluorescent material powder by means of a lamp that emits lighthaving a wavelength of 365 nm, it is confirmed that red color light isemitted.

FIG. 9 is a graph showing a light emission spectrum of the obtainedfluorescent material powder; the vertical axis is the relative lightemission intensity (arbitrary unit), while the horizontal axis is thewavelength (nm). The light emission spectrum when exciting, by means ofthe light of 450 nm, the fluorescent material powder shown in FIG. 9 areresults of measurement using the F-4500 (from Hitachi, Ltd.). As to thechromaticity coordinates of the light emission spectrum shown in FIG. 9,(x, y)=(0.657, 0.340), the peak wavelength is 649 nm, and the half widthis 90 nm.

Besides, the internal quantum efficiency of the fluorescent materialshown in the present comparative production example 2, which is measuredby a measurement system obtained by combining the MCPD-7000 and anintegrating sphere with each other, is 80%.

[2] Production of Semiconductor Light-Emitting Device

Examples 1 to 15

A silicone resin (product name: the KER2500, Shin-Etsu Chemical Co.,Ltd.) is used, each fluorescent material shown in a table 2 and thesilicone resin are mixed and dispersed at mass ratios shown in a table 3to produce mold resins, and a semiconductor light-emitting device foreach example having the structure shown in FIG. 1 is produced.

In the meantime, as the semiconductor light-emitting element, an LED(product name: the EZR, Cree, Inc.) having a light emission peakwavelength shown in the table 2 is used, and respective ratios among theresin, the orange fluorescent material, and the green fluorescentmaterial are suitably adjusted such that the color temperature of thelight-emitting device is about 5000K.

TABLE 2 BLUE LED PEAK GREEN WAVELENGTH ORANGE FLUORESCENT FLUORESCENTRED FLUORESCENT (nm) MATERIAL MATERIAL MATERIAL EXAMPLE 1 460 PRODUCTIONPRODUCTION NOT USED EXAMPLE 1-1 EXAMPLE 2-1 EXAMPLE 2 460 PRODUCTIONPRODUCTION NOT USED EXAMPLE 1-2 EXAMPLE 2-1 EXAMPLE 3 460 PRODUCTIONPRODUCTION NOT USED EXAMPLE 1-1 EXAMPLE 2-2 EXAMPLE 4 460 PRODUCTIONPRODUCTION NOT USED EXAMPLE 1-2 EXAMPLE 2-2 EXAMPLE 5 460 PRODUCTIONPRODUCTION NOT USED EXAMPLE 1-1 EXAMPLE 2-3 EXAMPLE 6 460 PRODUCTIONPRODUCTION NOT USED EXAMPLE 1-2 EXAMPLE 2-3 EXAMPLE 7 460 PRODUCTIONPRODUCTION NOT USED EXAMPLE 1-1 EXAMPLE 2-4 EXAMPLE 8 460 PRODUCTIONPRODUCTION NOT USED EXAMPLE 1-2 EXAMPLE 2-4 EXAMPLE 9 450 PRODUCTIONPRODUCTION NOT USED EXAMPLE 1-2 EXAMPLE 2-1 EXAMPLE 10 450 PRODUCTIONPRODUCTION NOT USED EXAMPLE 1-1 EXAMPLE 2-2 EXAMPLE 11 450 PRODUCTIONPRODUCTION NOT USED EXAMPLE 1-2 EXAMPLE 2-2 EXAMPLE 12 450 PRODUCTIONPRODUCTION NOT USED EXAMPLE 1-1 EXAMPLE 2-3 EXAMPLE 13 450 PRODUCTIONPRODUCTION NOT USED EXAMPLE 1-2 EXAMPLE 2-3 EXAMPLE 14 450 PRODUCTIONPRODUCTION NOT USED EXAMPLE 1-1 EXAMPLE 2-4 EXAMPLE 15 450 PRODUCTIONPRODUCTION NOT USED EXAMPLE 1-2 EXAMPLE 2-4 COMPARATIVE 460 COMPARATIVEPRODUCTION NOT USED EXAMPLE 1 PRODUCTION EXAMPLE 1 EXAMPLE 2-1COMPARATIVE 460 COMPARATIVE PRODUCTION COMPARATIVE EXAMPLE 2 PRODUCTIONEXAMPLE 1 EXAMPLE 2-1 PRODUCTION EXAMPLE 2 COMPARATIVE 460 NOT USEDPRODUCTION COMPARATIVE EXAMPLE 3 EXAMPLE 2-1 PRODUCTION EXAMPLE 2COMPARATIVE 450 COMPARATIVE PRODUCTION NOT USED EXAMPLE 4 PRODUCTIONEXAMPLE 1 EXAMPLE 2-1 COMPARATIVE 450 COMPARATIVE PRODUCTION COMPARATIVEEXAMPLE 5 PRODUCTION EXAMPLE 1 EXAMPLE 2-1 PRODUCTION EXAMPLE 2COMPARATIVE 450 NOT USED PRODUCTION COMPARATIVE EXAMPLE 6 EXAMPLE 2-1PRODUCTION EXAMPLE 2

TABLE 3 GREEN FLUORESCENT GREEN FLUORESCENT MATERIAL/ORANGE MATERIAL/REDRESIN/FLUORESCENT FLUORESCENT MATERIAL FLUORESCENT MATERIAL MATERIALRATIO RATIO RATIO EXAMPLE 1 11.25 1.38 0.00 EXAMPLE 2 10.66 1.51 0.00EXAMPLE 3 11.44 1.18 0.00 EXAMPLE 4 10.92 1.28 0.00 EXAMPLE 5 8.88 1.910.00 EXAMPLE 6 8.12 2.20 0.00 EXAMPLE 7 7.42 1.75 0.00 EXAMPLE 8 7.142.52 0.00 EXAMPLE 9 9.94 1.65 0.00 EXAMPLE 10 10.69 1.26 0.00 EXAMPLE 1110.24 1.36 0.00 EXAMPLE 12 7.64 2.25 0.00 EXAMPLE 13 6.95 2.60 0.00EXAMPLE 14 6.85 2.25 0.00 EXAMPLE 15 6.49 3.03 0.00 COMPARATIVE 12.420.97 0.00 EXAMPLE 1 COMPARATIVE 12.42 1.89 7.87 EXAMPLE 2 COMPARATIVE15.28 0.00 4.00 EXAMPLE 3 COMPARATIVE 11.33 1.13 0.00 EXAMPLE 4COMPARATIVE 11.49 2.13 8.50 EXAMPLE 5 COMPARATIVE 14.14 0.00 4.47EXAMPLE 6

FIGS. 10 to 24 show light emission spectra of the respectivelight-emitting devices in the examples 1 to 15. In the meantime, thelight emission spectra shown in FIGS. 10 to 24 are measured by using theMCPD-7000 (from Otsuka Electronics Co., Ltd.).

Example 16

A silicone resin (product name: the KER2500, Shin-Etsu Chemical Co.,Ltd.) is used, each fluorescent material shown in a table 4 and thesilicone resin are mixed and dispersed at mass ratios shown in the table4 to produce a mold resin, and a semiconductor light-emitting device forthe example 16 s produced.

In the meantime, in the example 16, as the semiconductor light-emittingelement, an LED (product name: the EZR, Cree, Inc.) having a lightemission peak wavelength at 450 nm is used, and the resin/fluorescentmaterial ratio is suitably adjusted such that the chromaticity pointapproaches a black body locus when the color temperature of thelight-emitting device is near 5000K.

A table 5 shows light-emitting properties of the respectivelight-emitting devices produced in the above example 16 and the above 9,while a table 6 shows properties of the Eu-activated α SiAlONfluorescent material used. In the meantime, each index shown in thetable 5 is calculated based on the spectrum measured by the MCPD-7000.

According to the table 5 and the table 6, as to the semiconductorlight-emitting device shown in the example 9, the light emissionproperty of the fluorescent material used is similar to the example 16,however, the color rendering property is improved. As shown in the table6, it is conceivable this is because the particle shapes such as theaverage particle diameter, specific surface area and the like of theEu-activated α SiAlON fluorescent material that is the orangefluorescent material are different.

The Eu-activated α SiAlON fluorescent material produced in theproduction example 1-2 and used in the example 9, as shown in the table6, is large in average particle diameter and small in specific surfacearea compared with the Eu-activated α SiAlON fluorescent materialproduced in the production example 1-3 and used in the example 16. Morespecifically, the Eu-activated α SiAlON fluorescent material produced inthe production example 1-2 has an average particle diameter of 15.3 μmand a specific surface area of 0.38 m²/g, while the Eu-activated αSiAlON fluorescent material produced in the production example 1-3 hasan average particle diameter of 11.2 μm and a specific surface area of0.78 m²/g. Therefore, as to the Eu-activated α SiAlON fluorescentmaterial produced in the production example 1-2, it is conceivable thatthe dispersion state in the mold resin is different from theEu-activated α SiAlON fluorescent material produced in the productionexample 1-3.

When the dispersion state of the Eu-activated α SiAlON fluorescentmaterial in the mold resin is different, the scattering and absorptionstates of the orange fluorescent material for the blue light and greenlight change. It is conceivable that this change has an influence on thelight emission spectrum of the light-emitting device and improves thecolor rendering property of the semiconductor light-emitting deviceshown in the example 9.

Accordingly, to improve the color rendering property, it is preferablethat the average particle diameter of the Eu-activated α SiAlONfluorescent material is 15 μm or more, and it is preferable that thespecific surface area is 0.4 m²/g or smaller. Besides, generally, thesmall specific surface area means that the particle diameters of theindividual particles composing the fluorescent material are large andthe uniformity of the crystal is high; when the uniformity of thecrystal is high, the luminous efficiency of the fluorescent materialrises. Therefore, making the specific surface area small to 0.4 m²/g orsmaller contributes to the improvement of the luminous efficiency aswell.

TABLE 4 GREEN FLUORESCENT MATERIAL/ ORANGE ORANGE GREEN RESIN/FLUORESCENT FLUORESCENT FLUORESCENT FLUORESCENT MATERIAL MATERIALMATERIAL MATERIAL RATIO RATIO EXAMPLE 16 PRODUCTION PRODUCTION 13.071.20 EXAMPLE1-3 EXAMPLE2-1

TABLE 5 BLUE LED PEAK WAVELENGTH (nm) Ra = R9 = TCP = Duv = x = y = R10= R11 = R12 = R13 = R14 = R15 = EXAMPLE 450 72.6 3.6 5010.9 −0.1 0.3450.351 35.6 70.0 32.6 74.2 81.5 73.6 9 EXAMPLE 450 69.4 −107 5013.7 −0.10.345 0.351 30.6 62.0 27.6 69.9 81.5 69.4 16

TABLE 6 Eu-ACTIVATED α SiAlON Eu-ACTIVATED β SiAlON LIGHT LIGHT EMISSIONEMISSION SPECTRUM SPECIFIC AVERAGE SPECTRUM SPECIFIC AVERAGE PEAKSURFACE PARTICLE PEAK SURFACE PARTICLE PRODUCTION WAVELENGTH AREADIAMETER PRODUCTION WAVELENGTH AREA DIAMETER EXAMPLE (nm) (m²/g) (μm)EXAMPLE (nm) (m²/g) (μm) EXAMPLE 9 PRODUCTION 610 0.38 15.3 PRODUCTION540 0.80 9.2 EXAMPLE 1-2 EXAMPLE 2-1 EXAMPLE 16 PRODUCTION 610 0.78 11.2PRODUCTION 540 0.80 9.2 EXAMPLE 1-3 EXAMPLE 2-1

Comparative Examples 1 to 6

A silicone resin (product name: the KER2500, Shin-Etsu Chemical Co.,Ltd.) is used, and each fluorescent material shown in the table 2 andthe silicone resin are mixed and dispersed at the mass ratios shown inthe table 3 to produce mold resins, and semiconductor light-emittingdevices for comparative examples 1 to 6 having the structure shown inFIG. 1 are produced.

In the meantime, as the semiconductor light-emitting element, the LED(product name: the EZR, Cree, Inc.) having the light emission peakwavelength shown in the table 2 is used, and respective ratios among theresin, the orange fluorescent material, the green fluorescent materialand the red fluorescent material are suitably adjusted such that thecolor temperatures of the light-emitting devices approach 5000K. In themeantime, the comparative examples 1, 4 have a structure that does notinclude the red fluorescent material, and the comparative examples 3, 6have a structure that does not include the orange fluorescent material.The comparative examples 2, 5 correspond to the example disclosed in thepatent document 2.

FIGS. 25 to 30 show respective light emission spectra of thesemiconductor light-emitting devices in the comparative examples 1 to 6.In the meantime, the light emission spectra shown in FIGS. 25 to 30 aremeasured by using the MCPD-7000 (from Otsuka Electronics Co., Ltd.).

A table 7 shows light emission properties of the respectivelight-emitting devices produced in the above examples and comparativeexamples. In the meantime, each index shown in the table 7 is calculatedbased on the light emission spectra in FIG. 10 to FIG. 30. FIG. 31 showsa relationship between Ra and the theoretical limit of luminous efficacyrelated to the semiconductor light-emitting devices which are producedin the examples 1 to 8 and in the comparative examples 1 to 3 and inwhich the peak wavelength of the blue LED is 460 nm, FIG. 32 shows arelationship between Ra and the theoretical limit of luminous efficacyrelated to the semiconductor light-emitting devices which are producedin the examples 9 to 15 and in the comparative examples 4 to 6 and inwhich the peak wavelength of the blue LED is 450 nm.

TABLE 7 THEORETICAL BLUE LED LIMIT OF PEAK LUMINOUS WAVELENGTH EFFICACY(nm) (lm/W) Ra = R9 = TCP = Duv = x = EXAMPLE 1 460 280.1 75.5 −10.25021.3 −0.4 0.344 EXAMPLE 2 460 270.6 80.6 19.6 5011.1 0.3 0.345 EXAMPLE3 460 273.4 83.1 14.1 5021.1 0.2 0.345 EXAMPLE 4 460 260.5 90.7 53.75013.9 0.1 0.345 EXAMPLE 5 460 275.3 81.0 2.5 5058.5 0.5 0.344 EXAMPLE 6460 263.3 88.1 38.8 5048.1 −0.1 0.344 EXAMPLE 7 460 269.9 80.0 −3.65060.4 0.5 0.344 EXAMPLE 8 460 263.9 83.5 15.0 5033.0 0.0 0.344 EXAMPLE9 450 271.5 72.6 3.6 5010.9 −0.1 0.345 EXAMPLE 10 450 272.7 76.7 2.75029.9 −0.1 0.344 EXAMPLE 11 450 260.3 82.4 41.4 5036.1 0.1 0.344EXAMPLE 12 450 271.4 77.8 −5.9 5018.0 −0.1 0.345 EXAMPLE 13 450 259.783.9 29.6 5032.1 0.0 0.344 EXAMPLE 14 450 270.5 77.7 −18.3 5030.3 0.00.344 EXAMPLE 15 450 264.0 80.9 0.5 5037.5 −0.4 0.344 COMPARATIVE 460289.2 68.8 −46.7 5036.8 0.3 0.344 EXAMPLE 1 COMPARATIVE 460 245.9 81.543.8 5004.1 0.4 0.345 EXAMPLE 2 COMPARATIVE 460 203.4 88.0 53.9 5071.40.0 0.343 EXAMPLE 3 COMPARATIVE 450 290.2 62.4 −61.0 5042.2 0.0 0.344EXAMPLE 4 COMPARATIVE 450 246.7 72.8 28.5 5008.7 0.2 0.345 EXAMPLE 5COMPARATIVE 450 207.5 77.3 79.2 5064.6 0.1 0.343 EXAMPLE 6 y = R10 = R11= R12 = R13 = R14 = R15 = EXAMPLE 1 0.350 56.8 59.7 38.7 77.8 91.4 72.3EXAMPLE 2 0.352 61.4 69.2 41.8 83.8 89.9 80.6 EXAMPLE 3 0.352 70.9 78.248.9 86.5 94.1 79.6 EXAMPLE 4 0.352 80.0 91.0 55.1 95.8 92.6 91.3EXAMPLE 5 0.351 71.5 74.5 49.5 83.6 95.9 75.7 EXAMPLE 6 0.350 80.5 87.155.5 92.0 95.5 86.4 EXAMPLE 7 0.351 88.6 68.3 63.3 85.4 94.0 74.3EXAMPLE 8 0.351 89.5 75.0 64.0 88.7 96.0 79.5 EXAMPLE 9 0.351 35.6 70.032.6 74.2 81.5 73.6 EXAMPLE 10 0.351 47.6 79.0 43.6 78.4 86.1 74.0EXAMPLE 11 0.351 56.6 82.4 51.2 87.5 84.8 85.3 EXAMPLE 12 0.351 55.879.8 53.9 77.6 91.1 71.2 EXAMPLE 13 0.351 65.3 86.7 62.1 85.8 90.6 81.6EXAMPLE 14 0.351 65.0 71.6 59.3 77.0 95.7 68.7 EXAMPLE 15 0.350 67.778.2 61.7 80.7 95.3 73.9 COMPARATIVE 0.351 49.9 47.0 33.7 69.7 92.2 61.7EXAMPLE 1 COMPARATIVE 0.352 59.7 66.9 40.2 83.5 88.6 84.4 EXAMPLE 2COMPARATIVE 0.350 72.1 86.4 47.9 98.6 82.9 85.5 EXAMPLE 3 COMPARATIVE0.351 23.1 51.4 22.2 60.4 83.9 55.2 EXAMPLE 4 COMPARATIVE 0.352 33.568.1 30.2 73.9 80.0 77.8 EXAMPLE 5 COMPARATIVE 0.350 43.3 78.8 37.4 87.874.6 96.1 EXAMPLE 6

TABLE 8 RELATIVE RELATIVE LED THEORETICAL LUMINOUS INTENSITY/ RELATIVELED LIMIT OF RELATIVE LUMINOUS LUMINOUS THEORETICAL LIMIT OF INTENSITYEFFICACY LUMINOUS EFFICACY EXAMPLE 1 100.0% 100.0% 1.00 EXAMPLE 2 94.7%96.6% 0.98 EXAMPLE 3 96.6% 97.6% 0.99 EXAMPLE 4 90.2% 93.0% 0.97 EXAMPLE5 93.4% 98.3% 0.95 EXAMPLE 6 88.4% 94.0% 0.94 EXAMPLE 7 89.6% 96.4% 0.93EXAMPLE 8 86.7% 94.2% 0.92 EXAMPLE 9 95.0% 96.9% 0.98 EXAMPLE 10 95.4%97.4% 0.98 EXAMPLE 11 90.2% 92.9% 0.97 EXAMPLE 12 91.1% 96.9% 0.94EXAMPLE 13 86.2% 92.7% 0.93 EXAMPLE 14 88.9% 96.6% 0.92 EXAMPLE 15 85.8%94.3% 0.91 COMPARATIVE EXAMPLE 1 103.4% 103.2% 1.00 COMPARATIVE EXAMPLE2 72.0% 87.8% 0.82 COMPARATIVE EXAMPLE 3 61.0% 72.6% 0.84 COMPARATIVEEXAMPLE 4 103.6% 103.4% 1.00 COMPARATIVE EXAMPLE 5 71.3% 88.1% 0.81COMPARATIVE EXAMPLE 6 63.0% 74.1% 0.85

Here, with reference to FIG. 31 and FIG. 32, distinctive effects of thepresent invention are described. According to FIG. 31 and FIG. 32, it isunderstood that there is a trade-off relationship that when Raincreases, the theoretical limit of luminous efficacy declines; however,it is understood that compared with the semiconductor light-emittingdevices in the comparative examples shown by triangles in the figure,the semiconductor light-emitting devices in the examples shown by blackdots in the figure are influenced by the trade-off remarkably slightly.This tendency is conspicuous especially in a region where Ra is 80 ormore, and it is understood that the semiconductor light-emitting devicesin the examples have a structure which shows remarkably high luminousefficiency in a region of practical color rendering property.

In a table 8, the theoretical limits of luminous efficacy and relativevalues of the LED luminous intensity of the respective light-emittingdevices produced in the above examples and comparative examples arecompared with each other. The LED luminous intensity shown in the table8 is measured by means of a structure obtained by combining theMCPD-7000 and an integrating sphere under a drive condition of a voltageof 5 V, an electric current of 20 mA.

According to the table 8, it is understood that there is a strongcorrelation between the actual measured values of the LED luminousintensity and the theoretical limits of luminous efficacy in theexamples and comparative examples. In other words, it is understood thatin the structure having the high theoretical limit of luminous efficacyin the present invention, the actual LED luminous intensity also becomeshigh.

However, the relative LED luminous intensity/relative theoretical limitof luminous efficacy ratios in the comparative examples 2, 3, 5 and 6are lower than in the examples. In other words, in the semiconductorlight-emitting devices produced in the comparative examples 2, 3, 5 and6, the actual measured values of the LED luminous intensity are lowerthan the LED luminous intensity predicted by theoretical calculation.This is because the semiconductor light-emitting devices produced in thecomparative examples 2, 3, 5 and 6 in the table 8 use the redfluorescent material; the green fluorescent material absorbs the orangelight, besides, the red fluorescent material also absorbs the greenlight and the orange light; therefore, a two-step conversion lossoccurs; accordingly, the luminous efficiency of the light-emittingdevices decline. In the meantime, in the table 8, the comparativeexample 1 and the comparative example 4 are higher than the examples inLED luminous intensity; however, as shown in the table 7, thecomparative example 1 and the comparative example 4 have Ra of 70 orsmaller and R9 of −40 or smaller, that is, the color rendering propertyis remarkably low. Therefore, in the comparative example 1 and thecomparative example 4, the LED luminous intensity is high, but the colorrendering property is not preferable in practical use.

As described above, in the light-emitting devices shown in the examples,the cross absorption among the fluorescent materials is slight comparedwith the light-emitting devices shown in the comparative examples,accordingly, the luminous efficiency is high. This tendency isconspicuous especially in the examples 1 to 4 and the examples 9 to 11,and in these examples, the relative LED luminous intensity/relativetheoretical limit of luminous efficacy ratio is 0.97 or more that isespecially high. This is because the green fluorescent materials used inthe examples 1 to 4 and the examples 9 to 11 are the Eu-activated βSiAlON fluorescent materials shown in the production examples 2-1 and2-2. In the Eu-activated β SiAlON fluorescent material, the half widthof the light emission spectrum is 70 nm or smaller that is narrow,accordingly, the overlapping between the absorption spectrum of theorange fluorescent material and the absorption spectrum of the greenfluorescent material becomes small, whereby the cross absorption betweenthe fluorescent materials is especially alleviated.

Besides, according to the table 3 and the table 8, it is understood thatin a case where the semiconductor light-emitting devices having the samepeak wavelength of the blue LED and the same orange fluorescent materialare compared with each other, the semiconductor light-emitting devicesusing the green fluorescent material in the production example 2-2 havethe highest Ra. This shows that the Eu-activated β SiAlON fluorescentmaterial shown in the production example 2-2 has an especiallypreferable light emission spectrum when combined with the orangefluorescent material according to the present invention.

Comparative Examples 7 to 9

A silicone resin (product name: the KER2500, Shin-Etsu Chemical Co.,Ltd.) is used, and each fluorescent material shown in a table 9 and thesilicone resin are mixed and dispersed at the mass ratios shown in atable 10 to produce mold resins, and semiconductor light-emittingdevices for respective comparative examples having the structure shownin FIG. 1 are produced.

In the meantime, as the semiconductor light-emitting element, an LED(product name: the EZR, Cree, Inc.) having the light emission peakwavelength at 460 nm is used, and respective ratios among the resin, theorange fluorescent material, and the green fluorescent material aresuitably adjusted such that the color temperatures of the light-emittingdevices approach 5000K.

FIGS. 33 to 35 show respective light emission spectra of thesemiconductor light-emitting devices in the comparative examples 7 to 9.In the meantime, the light emission spectra shown in FIGS. 33 to 35 aremeasured by using the MCPD-7000 (from Otsuka Electronics Co., Ltd.).

TABLE 9 BLUE LED PEAK WAVELENGTH ORANGE FLUORESCENT GREEN FLUORESCENT(nm) MATERIAL MATERIAL COMPARATIVE 460 COMPARATIVE PRODUCTION EXAMPLE 7PRODUCTION EXAMPLE 1 EXAMPLE 2-2 COMPARATIVE 460 COMPARATIVE PRODUCTIONEXAMPLE 8 PRODUCTION EXAMPLE 1 EXAMPLE 2-3 COMPARATIVE 460 COMPARATIVEPRODUCTION EXAMPLE 9 PRODUCTION EXAMPLE 1 EXAMPLE 2-4

TABLE 10 GREEN FLUORESCENT RESIN/ MATERIAL/ORANGE FLUORESCENTFLUORESCENT MATERIAL RATIO MATERIAL RATIO COMPARATIVE 12.64 0.85 EXAMPLE7 COMPARATIVE 11.40 1.08 EXAMPLE 8 COMPARATIVE 5.71 0.69 EXAMPLE 9

Comparative Example 10

A silicone resin (product name: the KER2500, Shin-Etsu Chemical Co.,Ltd.) is used, and a commercial Ce-activated YAG fluorescent material(product name: the P46-Y3, Kasei Optonix, LTD., the light emission peakwavelength of 568 nm, the half width of 129 nm, the chromaticitycoordinates (x, y)=(0.613, 0.386)) and the silicone resin are mixed anddispersed at a mass ratio of the resin/fluorescent material=11.7 toproduce a mold resin, and a semiconductor light-emitting device for acomparative example 10 having the structure shown in FIG. 1 is produced.

In the meantime, as the semiconductor light-emitting element, an LED(product name: the EZR, Cree, Inc.) having a light emission peakwavelength at 460 nm is used, and the resin/fluorescent material ratiois suitably adjusted such that the chromaticity point approaches a blackbody locus when the color temperature of the light-emitting device isnear 5000K.

FIG. 36 shows a light emission spectrum of the semiconductorlight-emitting device in the comparative example 10. In the meantime,the light emission spectrum shown in FIG. 36 is measured by using theMCPD-7000 (from Otsuka Electronics Co., Ltd.).

A table 11 shows light emission properties of the respectivelight-emitting devices produced in the above examples and comparativeexamples. In the meantime, each index shown in the table 11 iscalculated based on the light emission spectra in FIG. 33 to FIG. 36.FIG. 37 shows a relationship between the light emission peak wavelengthand the color rendering property of the orange fluorescent materialsrelated to the examples 1 to 8 and to the comparative examples 1, 7 to9. Besides, FIG. 38 shows a relationship between Ra and the theoreticallimit of luminous efficacy of the semiconductor light-emitting devicesrelated to the examples 1 to 8 and comparative examples 1, 7 to 10 shownin the table 11.

TABLE 11 Eu-ACTIVATED α SiAlON LIGHT EMISSION THEORETICAL SPECTRUM LIMITOF PEAK LUMINOUS PRODUCTION WAVELENGTH EFFICACY COLOR EXAMPLE (nm)(lm/W) Ra R9 TEMPERATURE EXAMPLE 1 PRODUCTION 597 280.1 75.5 −10.25021.3 EXAMPLE 1-1 EXAMPLE 3 PRODUCTION 597 273.4 83.1 14.1 5021.1EXAMPLE 1-1 EXAMPLE 5 PRODUCTION 597 275.3 81.0 2.5 5058.5 EXAMPLE 1-1EXAMPLE 7 PRODUCTION 597 269.9 80.0 −3.6 5060.4 EXAMPLE 1-1 EXAMPLE 2PRODUCTION 610 270.6 80.6 19.6 5011.1 EXAMPLE 1-2 EXAMPLE 4 PRODUCTION610 260.5 90.7 53.7 5013.9 EXAMPLE 1-2 EXAMPLE 6 PRODUCTION 610 263.388.1 38.8 5048.1 EXAMPLE 1-2 EXAMPLE 8 PRODUCTION 610 263.9 83.5 15.05033.0 EXAMPLE 1-2 COMPARATIVE COMPARATIVE 585 289.2 68.8 −47 5036.8EXAMPLE 1 PRODUCTION EXAMPLE 1 COMPARATIVE COMPARATIVE 585 284.7 73.1−33.0 5065.8 EXAMPLE 7 PRODUCTION EXAMPLE 1 COMPARATIVE COMPARATIVE 585285.9 72.0 −39 5022.7 EXAMPLE 8 PRODUCTION EXAMPLE 1 COMPARATIVECOMPARATIVE 585 283.6 71.6 −41 5042.4 EXAMPLE 9 PRODUCTION EXAMPLE 1COMPARATIVE Ce-ACTIVATED YAG 266.0 74.9 −7 4552.2 EXAMPLE 10 FLUORESCENTMATERIAL Duv = x = y = R10 = R11 = R12 = R13 = R14 = R15 = EXAMPLE 1−0.4 0.344 0.350 56.8 59.7 38.7 77.8 91.4 72.3 EXAMPLE 3 0.2 0.345 0.35270.9 78.2 48.9 86.5 94.1 79.6 EXAMPLE 5 0.5 0.344 0.351 71.5 74.5 49.583.6 95.9 75.7 EXAMPLE 7 0.5 0.344 0.351 88.6 68.3 63.3 85.4 94.0 74.3EXAMPLE 2 0.3 0.345 0.352 61.4 69.2 41.8 83.8 89.9 80.6 EXAMPLE 4 0.10.345 0.352 80.0 91.0 55.1 95.8 92.6 91.3 EXAMPLE 6 −0.1 0.344 0.35080.5 87.1 55.5 92.0 95.5 86.4 EXAMPLE 8 0.0 0.344 0.351 89.5 75.0 64.088.7 96.0 79.5 COMPARATIVE 0.3 0.344 0.351 49.9 47.0 33.7 69.7 92.2 61.7EXAMPLE 1 COMPARATIVE 0.2 0.343 0.351 58.3 57.5 40.0 74.8 94.0 65.9EXAMPLE 7 COMPARATIVE 0.1 0.345 0.351 59.1 55.6 40.9 73.3 94.6 63.8EXAMPLE 8 COMPARATIVE 0.2 0.344 0.351 64.5 52.0 44.5 73.7 95.2 63.2EXAMPLE 9 COMPARATIVE 0.1 0.359 0.362 57.0 57.7 34.5 76.0 92.5 70.3EXAMPLE 10

Here, with reference to FIG. 37, a peak wavelength range of the orangefluorescent material in the present invention is described. According toFIG. 37, it is understood that Ra improves as the peak wavelength of theorange fluorescent material becomes longer, and Ra improves sharplyespecially at wavelengths of 595 nm or longer. In other words, as to thepeak wavelength of the orange fluorescent material used in thelight-emitting device, it is shown that there is an inflection point at595 nm where the color rendering property improves sharply.

Next, with reference to FIG. 38, a peak wavelength range of the orangefluorescent material in the present invention preferable in practicaluse is described. According to FIG. 38, Ra of the light-emittingdevices, in which the light emission peak wavelength of the orangefluorescent material is 595 nm or smaller, deteriorates compared withthe semiconductor light-emitting devices that use the Ce-activated YAGonly. As described above, the light-emitting device obtained bycombining the Ce-activated YAG only with the semiconductorlight-emitting device does not have sufficient color rendering propertyfor general illumination. In other words, the light-emitting devices, inwhich the light emission peak wavelength of the orange fluorescentmaterial is 595 nm or smaller, do not have the color rendering propertysufficient in practical use. In contrast, the light-emitting devices, inwhich the light emission peak wavelength of the orange fluorescentmaterial is 595 nm or more, have the color rendering property higherthan the Ce-activated YAG, further, the theoretical limit of luminousefficacy also is higher than the light-emitting devices that use theCe-activated YAG. Therefore, in the light-emitting device shown in thepresent example, the luminous efficiency and the color renderingproperty are higher than the conventional combination, and thelight-emitting device is highly practical.

Further, when the light emission peak wavelength of the orangefluorescent material becomes 605 nm or more, the light-emitting devicesatisfies Ra>80 at the substantially same theoretical limit efficiencyas the light-emitting device that uses the Ce-activated YAG fluorescentmaterial, accordingly, satisfies the JIS standards for the aboveillumination, and further preferable in practical use as thelight-emitting device that has the high luminous efficiency. Inaddition, R9 is not especially defined in the JIS standards and thelike; however, by using the orange fluorescent material of 595 nm ormore, R9>0 is obtained, which is a preferable feature in practical use.As described above, if R9 has a negative value such as −5 or smaller andthe like, the recolor looks insufficiently, accordingly, in a case ofbeing used in home illumination devices and the like, for example,disadvantages that human skin colors look unnaturally and the likeoccur.

INDUSTRIAL APPLICABILITY

The semiconductor light-emitting device according to the presentinvention is high in luminous efficiency and emits white light thatshows high Ra and R9. Because of this, the semiconductor light-emittingdevice according to the present invention is usable in variousillumination devices such as a home illumination device, a vehicleillumination device and the like.

REFERENCE SIGNS LIST

-   -   1 semiconductor light-emitting device    -   2 semiconductor light-emitting element    -   3 printed wiring board    -   4 resin frame    -   5 mold resin    -   6 InGaN layer    -   7 p side electrode    -   8 n side electrode    -   9 n electrode portion    -   10 adhesive    -   11 p electrode portion    -   12 metal wire    -   13 orange fluorescent material    -   14 green fluorescent material

The invention claimed is:
 1. A lighting device comprising: asemiconductor light-emitting element for emitting a blue light having apeak wavelength in a range of 420 to 480 nm; and a fluorescent materialretainer including: a first fluorescent material composed of cerium,lutetium, aluminum and oxygen, for absorbing the blue light to emit alight having a first peak wavelength in a range of 500 to 550 nm, and asecond fluorescent material which is a Eu-activated α SiAlON fluorescentmaterial and which is composed of europium, calcium, silicon, aluminum,oxygen and nitrogen, for absorbing the blue light to emit a light havinga second peak wavelength in a range of 595 to 620 nm, wherein the firstfluorescent material is a green fluorescent material and the secondfluorescent material is an orange fluorescent material.
 2. The lightingdevice of claim 1, wherein the second peak wavelength is 597 nm.
 3. Thelighting device of claim 1, wherein the first and second fluorescentmaterials are dispersed in the fluorescent material retainer.
 4. Thelighting device of claim 1, wherein a particle of the second fluorescentmaterial has a diameter that is at most 20 μm.
 5. The lighting device ofclaim 4, wherein a particle of the first fluorescent material has adiameter that is at most 20 μm.
 6. The lighting device of claim 1,wherein the first fluorescent material is Ce activated Lu3Al5O12.
 7. Thelighting device of claim 1, wherein a ratio of the first fluorescentmaterial and the second fluorescent material is adjusted such that acolor temperature of a light emitted from the lighting device is about5000K.
 8. The lighting device of claim 1, wherein the second peakwavelength is in a range of 605 to 620 nm.